Although you may have spent years building up a successful enterprise, your family may be forced to sell it soon after your death to pay the federal estate-tax bill. The full amount of estate tax is due nine months after an individual’s death. Fortunately, there is some tax relief for a family that inherits a small business.

Timely tax break: If the estate qualifies, the family can elect to pay no tax on the business interest for five years. And subsequent payments can be stretched out over 10 years. Result: Your family can take up to 15 years to pay the tax. (Actually, it’s 14 years, since the due date for the last installment of interest coincides with the first installment of tax.)

There is, however, one catch. Interest must be paid each year on the unpaid portion of the tax. But the estate pays only 2% on the tax attributable to the first $1 million of the taxable value of the business interest. The interest rate for tax underpayments applies to any amount above $1 million (subject to inflation indexing). The threshold for 2016 is $1.48 million.

When does an estate qualify for the 15-year deferral? Generally speaking, the business must constitute at least 35% of the adjusted gross estate. Your adjusted gross estate is the gross estate less any expenses, debts and losses.

In addition, you must have operated the business as one of the following: (1) a sole proprietor; (2) a partner with an interest of 20% or more in the partnership, or with an interest in a partnership that has no more than 45 partners; or (3) a corporate stockholder owning 20% or more of the voting stock, or owning stock in a corporation with no more than 45 shareholders.

Finally, a proper notice of election must be attached to a timely estate-tax return.

Unfortunately, the benefit of this special provision may be lost if all the i’s aren’t dotted and the t’s aren’t crossed. Don’t hesitate to ask your professional advisers for assistance.